1. Field of the Invention
The present invention relates generally to pollutant removal from industrial gas outputs and more particularly to a multi-stage collector for multi-pollutant control.
2. Description of the Prior Art
Ever increasing energy consumption is a fact of life. Unfortunately, the energy producing industry is inevitably associated with emissions of vast amounts of dust, heavy metals such as mercury and various harmful gaseous contaminants such as sulfur dioxide and oxides of nitrogen. These two gases are major anthropogenic acid gases that lead to the formation of acid precipitation and photochemical smog and have an adverse effect on human health and on vegetation.
Traditionally, individual removal of either sulfur oxides (SO2) or nitrous oxides (NOx) can be achieved by independent air pollution control devices. For large scale emitters, Flue Gas Desulphurization (FGD) is the state of the art control technology for SO2 removal, while Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) serve as technologies for NOx removal. Unfortunately, SO2 and NOx coexist in flue gases in many cases, such as the combustion of heavy oil, diesel fuel and coal. The need for separate removal of pollutants is a major weakness of current methods. It would be extremely advantageous and cost-effective to have an efficient technology for simultaneous removal of multiple pollutants like SO2, NOx and heavy metals like Hg. Such a simultaneous technology would result in a great reduction of capital expenditure and a great reduction in space needed by power plants.
Non-thermal plasma at atmospheric pressure can be used effectively as part of such simultaneous technology. Many types of non-thermal plasma reactors for processing of exhausted gases have been developed. At the heart of these devices is generally a plasma source that generates many chemically active species such as (O, OH, HO2 etc.) in treated gases at atmospheric pressure without essentially heating the gases. Dielectric barrier discharge (DBD), and pulsed corona discharge (PCD), are well known as such plasma sources. However these types of discharges have intrinsic limitations associated with necessity to use narrow inter-electrode gaps and short high voltage pulses for the DBD and PCD respectively that results in difficulties in introducing these sources into real practice.
Krigmont in U.S. Pat. Nos. 6,524,369, and 6,932,857 teaches several new concepts for simultaneous particulate and gas removal from effluent gases through the use of steady-state corona discharge, electrostatic precipitation and barrier filtration. The present invention is an extension of the principles taught in these patents. Applications Ser. Nos. 6,524,369 and 6,932,857 are hereby incorporated by reference. This technology can be successfully used for controlling volatile organic compounds as well (instead of the normal approaches based on thermal incineration, catalytic oxidation and carbon absorption).